No self-respecting modern handheld console can afford to exist without an equivalent of the App Store, and Nintendo's DSiWare download service is one of the prime justifications for buying a DSi rather than an older variant of the DS. DSiWare had a bit of a slow start (Nintendo's certification process is notoriously bureaucratic and stringent), but it is starting to develop a decent library of value-for-money games, among which are some hidden gems.

Super Yum Yum Puzzle Adventures, developed and published by British companies, looks like a kids' game at first glance, but soon reveals unexpected depth. Its premise is simple: you control Leon, a chameleon with a long tongue and an insatiable appetite for different-coloured fruit. He can reach otherwise inaccessible areas by extending his tongue horizontally or vertically and pulling himself across to fruit which are the same colour as him. He then gobbles the fruit and changes to whatever colour its leaves happen to be.

This classic puzzle mechanic has some extra layers of complexity – some levels have raised areas, and if Leon is on a platform, he can't gobble ground-level fruit. Dotted around the levels are Leon's babies, and he will often have to rescue a certain number before acquiring the combined eating-power to tackle certain (helpfully labelled) larger fruit. If you find yourself in a cul-de-sac, you can rewind move by move. The game sprawls across four worlds with 12 levels each, and moving to a newly opened world involves negotiating a rhythm-action mini-game.

If you want to check out what DSiWare is all about, Super Yum Yum Puzzle Adventures provides the perfect introduction. It's deceptively simple, cheap (800 Nintendo Points equates to around £7.50), yet as substantial as the average DS cartridge, and once you tune into its unique puzzle-language, it proves to be surprisingly challenging and fiercely addictive. Earlier (albeit less meaty) versions of it are available from Apple's App Store, too. But at last, it seems as though Nintendo's DSiWare is beginning to acquire some credibility.